Bromthymol blue (BTB) is a chemical indicator that is yellow in acidic solutions and blue in basic solutions. Since carbon dioxide in solution produces carbonic acid, BTB is yellow in the presence of sufficient carbon dioxide.
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This is the scoring guide for our answers.
Question 1
1.
What is a substance? (look up the definition if you're not sure)
Question 2
2.
Do your observations from Part A provide
evidence that air is a substance? Why or
why not?
Use this information and the table to answer question #3.
Question 3
3.
Is the air that comes out of your lungs the same as your classroom air?
Explain.
Question 4
4.
Is air a substance or is it just empty space?
Support your answer with evidence
from this investigation.
Question 5
5.
Extension: Plan an experiment or demonstration to provide more evidence that air
is a substance.
